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The Effects of Elevated Testosterone on the Outcome of
ma2009 H1N1 Influenza A Virus infection in Old Male Mice
by
Ornob Alam
A thesis submitted to Johns Hopkins University in conformity with the
requirements for the degree of Master of Science
Baltimore, Maryland
April, 2015
ii
ABSTRACT
Testosterone (T) has anti‐inflammatory properties, and has been shown to play a
role in the pathogenesis of infectious and autoimmune diseases. Disease pathology from
influenza A virus (IAV) infection is caused by an excessive pro‐inflammatory response,
and severe disease is especially common among elderly men, who have lower T levels.
We tested the hypothesis that T will protect against IAV pathogenesis in young adult (8‐
10 weeks) and old (17‐18 months) male mice. To study the effects of T in young adult
male mice, the mice were gonadectomized, treated with T or placebo capsules, infected
with a sub‐lethal dose of H1N1, and monitored for morbidity and mortality. In old male
mice, serum T is naturally low, therefore gonadectomies are not required before the
subsequent steps. In addition, we attempted to elevate testosterone levels
endogenously in old male mice through steroidogenic drugs called TSPO ligands.
However, two different drugs tested did not significantly raise serum testosterone
levels. T‐treated young adult males experienced lower morbidity, and had lower IgG
antibody titers compared to placebo‐treated young adult males. In old males, while the
same dose of T was not protective against morbidity from IAV infection, treatment with
a higher dose of T resulted in improved recovery from influenza disease. Protection
from morbidity by testosterone treatment is not reflected in the expression of Ki67,
which is a marker for proliferation, in the lungs at 21 days after infection. This suggests
that either the improved recovery from disease is not associated with improved repair,
or day 21, which is after peak disease and viral clearance, is too late a time point to
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detect any difference. We hypothesize that old males require a higher dose of T in order
to mitigate the chronic pro‐inflammatory state brought about by aging.
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ACKNOWLEDGEMENTS
I am delighted to take this opportunity to thank my thesis advisor, Dr. Sabra
Klein, for all the support and guidance during my time in her laboratory. I would like to
thank Landon vom Steeg and Olivia Hall for their great patience in teaching me almost
everything I know about working with mice, data analysis, and many other things. I
would like to thank Dr. Jackye Peretz for her help and advice with various techniques
and questions. I am grateful to all the members of the Klein and Pekosz laboratories for
their great input on my presentations and research, and for helping to create a work
environment that I have really enjoyed. I would like to thank my secondary reader, Dr.
Barry Zirkin, for all the discussions and help regarding my research and writing, and
members of his group, Dr. Haolin Chen, Janet Folmer, and June Liu for the numerous
occasions on which they have helped me plan out my research, and learn new
techniques. Lastly, I would like to thank my father, mother, sister, and friends for all
their love and support throughout my life.
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TABLE OF CONTENTS
Title Pg.
Introduction 1‐11
Influenza Pathogenesis 1
Aging, the Immune System, and the Outcome of Infectious Diseases 3
Testosterone, the Immune System and Aging 6
Models for Studying the Effects of Testosterone in Old Male Mice 9
Methods
12‐16
Animals 12
Virus Infection and Quantification 12
TSPO Ligand Administration 13
Testosterone Administration 13
Sample Collection 14
Immunohistochemistry and Staining 14
Anti‐influenza total IgG ELISA 15
Statistical Analyses 16
Results
17‐25
Administration of testosterone results in reduced morbidity and antibody titers in young male mice following infection with influenza A virus
17
Administration of the TSPO Ligands Ro5‐4864 and PK11195 does not increase testosterone concentrations in old male mice
17
Administration of low dose testosterone does not alter the outcome of infection with ma2009 H1N1 in old male mice
18
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Administration of high dose testosterone improves the outcome of infection with ma2009 H1N1 in old male mice
19
Protection from influenza pathogenesis is not associated with increased proliferation in the lungs at 21 days post infection
20
Discussion
29‐36
Conclusions 29
Future Directions 33
Public Health Significance 35
Bibliography
37‐43
Curriculum Vita 44‐46
vii
LIST OF FIGURES
Results
Figure 1: Effects of testosterone (T) on the outcome of ma2009 H1N1 influenza infection in young male mice (2 mo)
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Figure 2: Effects of Ro5‐4864 and PK11195 on body mass, and serum and testicular testosterone (T) in old male mice
22
Figure 3: Effects of low dose testosterone (low T) on the outcome of ma2009 H1N1 influenza infection in old male mice (17 mo)
24
Figure 4: Effects of high dose testosterone (high T) on the outcome of ma2009 H1N1 influenza infection in old male mice (17 mo)
26
Figure 5: Effects of testosterone treatment on Ki67 expression 21 days post infection with ma2009 H1N1 influenza in young and old male mice
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1
INTRODUCTION
Influenza Pathogenesis
Influenza viruses are an enveloped viruses of the Orthomyxoviridae family with a
segmented, (‐) ssRNA genome (Baigent & McCauley, 2003). Influenza A, B, and C are the
three types of Orthomyxoviridae currently known to infect humans, with influenza A and
B being the most associated with severe disease (Baigent & McCauley, 2003). Influenza
disease is characterized by varying severity of febrile and respiratory symptoms (Lagace‐
Wiens et al., 2010). While illness from seasonal strains generally lasts one to two weeks,
influenza can also result in hospitalizations and death. The virus is transmitted through
respiratory droplets and primarily infects epithelial cells of the respiratory tract. The
disease is considered a worldwide public health problem because of the ability of the
virus to change every year, its rapid transmission between humans, and the resulting
pandemic potential (Lagace‐Wiens et al., 2010).
RNA genomes are especially susceptible to mutations due to the absence of
proofreading mechanisms during replication, as opposed to the proofreading and repair
mechanisms found in DNA viruses (Lauring et al., 2013). This allows RNA viruses to
evade immune systems and anti‐viral drugs by increasing the likelihood of a mutation
that confers resistance. Single nucleotide mutations that enable influenza viruses to
escape host immunity are referred to as antigenic drift (Bouvier & Palese, 2008). In
addition, the segmented nature of the influenza virus genome allows reassortment
between different strains of each viral species (Bouvier & Palese, 2008). For instance,
2
two influenza A strains, after coinfecting a host cell, can exchange segments; the
resulting recombinant strain can have altered replication rates, thereby contributing to
altered virulence (Pappas et al., 2008). This is known as antigenic shift. Influenza viruses
infect birds, pigs, and other animals alongside humans, and therefore segments
previously not seen in humans can arise through reassortment and human contact with
animals, and have unpredictable effects (Bouvier & Palese, 2008).
These mechanisms for genetic variation make influenza seasonal outbreaks a
logistical challenge as new vaccines need to be developed every year (Kidd, 2014).
Despite these efforts, seasonal influenza strains are still a significant cause of morbidity
as well as mortality, having been associated with an average of 23,640 deaths per year
in the US between 1976 and 2007 (CDC, 2010). There have also historically been
multiple pandemics of influenza as a result of new strains of the virus that arose that
were easily transmissible, and that the human population had no preexisting immunity
to. The 1918 influenza pandemic killed an estimated 50 million people around the world
(Taubenberger et al., 2012).
Populations that experience the greatest disease severity are children, the
elderly, pregnant women, and obese individuals which are all, to some degree,
immunocompromised populations (Mauskopf et al., 2013). Sex differences in disease
outcome have also been observed. Women of reproductive age (16‐49) are more
susceptible to severe disease from influenza infection, whereas among older individuals
(65+) men experience more severe disease (Klein, 2012). Influenza disease pathology is
primarily caused by a dysregulated inflammatory response (Damjanovic et al., 2012).
3
These differences in disease pathology are therefore thought to be a result of different
inflammatory environments possibly mediated by hormonal differences between the
groups of individuals as well as across the life course (Klein, 2012).
Aging, the Immune System, and the Outcome of Infectious Diseases
Immunosenescence refers to the progressive functional decline of the immune
system with age (Castelo‐Branco & Soveral, 2014). It is also associated with a chronic
low‐grade pro‐inflammatory state, which is thought to be a result of increased oxidative
stress in aging cells and elevated levels of certain pro‐inflammatory cytokines (Cannizzo
et al., 2011). Both the innate and adaptive arms of the immune system are affected.
Within the innate immune system, a few noteworthy changes are: 1)
plasmacytoid DCs (pDCs) undergo a decrease in the number of IFN‐α producing cells,
even though total numbers remain similar to younger age groups (Jing et al., 2009); 2)
monocyte‐derived DCs from aged subjects have increased reactivity to self‐antigens
such as DNA, which is thought to contribute to chronic inflammation during aging
(Agrawal et al., 2009); 3) monocytes undergo changes in the numbers of different
subpopulations, and also show a cumulative decline in the secretion of IL‐6 and TNF‐α
(Nyugen et al. 2010); and 4) neutrophils exhibit reduced phagocytic ability and
decreased bacteriocidal activity in the elderly (Wenisch et al., 2000).
Data on the adaptive immune system from animal models as well as humans
show that aging is associated with reduced clonal diversity of naïve CD4+ T cells (Naylor
4
et al., 2005), increased frequency of central memory, reduced frequency of effector
memory CD4+ T cells (Kang et al., 2004), reduced clonal diversity of CD8+ T cells
(Messaoudi et al., 2004), and increased frequency of effector memory and effector
CD8+ cells (Hong et al., 2004). Decrease in IL‐2 production during aging contributes to
decreased proliferation of all thymic‐derived T cells (Effros & Walford, 1983). The
decreased ability to proliferate and preserve T cell receptor (TCR) diversity likely
contributes to the reduced immune‐surveillance that results in increased susceptibility
to infectious diseases among aged individuals. CD4+ and CD8+ T cells from aged
individuals generally do not express the co‐stimulatory molecule CD28, and this is
thought to confer the cells with resistance to apoptosis (Vallejo et al., 2000). Loss of IL‐2
also results in increased IFN‐γ production from CD28null cells, which potentially
contributes to chronic inflammation during aging (Kared et al., 2014). Loss of IL‐2 in
conjunction with an increase in IL‐1β results in an increase in the number of T helper 17
cells (Th17) cells (Lim et al., 2014). This results in an increase in the basal
Th17/Regulatory T (Treg) cell ratio (Schmitt et al., 2013), even though the basal levels of
Treg cells do not vary significantly with age (Hwang et al., 2009). Dysregulation of Th17
responses possibly favors inflammation and contributes to age‐associated autoimmune
diseases. In contrast, the Th17/Treg cell ratio decreases with age after stimulation,
suggesting an increase in the production of suppressive cells after infection (Schmitt et
al., 2013). Increased activity of Treg cells could prevent rejection of tumor cells and
contribute to cancer (Fessler et al., 2013).
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Aging is also associated with changes in B cell function. Elderly individuals have
been shown to have decreased clonal diversity of B cells compared to young individuals
(Gibson et al., 2009). In a study conducted with an inactivated seasonal influenza
vaccine, antigen‐specific plasmablasts, as well as the number of antibodies produced by
each cell, were shown to be reduced in elderly individuals (70‐ to 100‐ years old) in
response to vaccination as compared to younger individuals (18‐ to 30‐ years old)
(Sasaki et al., 2011). However, antibodies induced by the vaccine in the elderly
individuals were shown to react with greater avidity and affinity to the 2009 pandemic
H1N1 virus than those in the young individuals. In a study conducted with an activated
split 2009 pandemic H1N1 vaccine, antibody levels and avidity were both shown to be
higher in elderly individuals (66‐ to 83‐ years old) than in young individuals (18‐ to 65‐
years old), possibly as a result of preexisting immunity to a related H1N1 strain in elderly
populations (Khurana et al., 2012). Receipt of seasonal influenza vaccine by
intramuscular injection results in significantly higher antibody titers in elderly (>65
years‐old) females than in elderly males (Engler et al., 2008). In addition, elderly (>65
years‐old) males have a higher incidence of severe disease from influenza after having
received the seasonal influenza vaccine (Wang et al., 2002). Therefore, while there
appears to be evidence for the general decline of B cell function with age, some data
also suggest that the qualitative antibody response is improved in elderly individuals,
and the functional changes vary by gender.
A mouse study on the lungs during aging showed that pulmonary macrophages
exist in a highly activated state in older mice (18 months) compared to younger mice (3
6
months) (Canan et al., 2014). The older mice were also shown to have elevated basal
levels of the pro‐inflammatory cytokines IFN‐γ, TNF‐α, and IL‐12 in the lungs. This
possibly contributes to the chronic inflammatory state associated with aging. In
response to Mycobacterium tuberculosis infection, pulmonary macrophages in the older
mice exhibited greater uptake of bacteria, but lower activation by IFN‐γ (Canan et al.,
2014). Another study showed that older mice (16‐18 months old) showed greater
morbidity from a sub‐lethal dose of influenza A virus than younger mice (2‐3 months)
(Yin et al., 2014). The study showed that this was at least partially caused by more
damage to alveolar Type I and Type II cells, and delayed epithelial repair. This supports
the existence of a chronic pro‐inflammatory environment in the lungs in aged mice.
Aging is therefore characterized by a weakened response to infections as a result
of a decline in function in the innate and adaptive arms of the immune system, as well
as a chronic low‐grade pro‐inflammatory state possibly brought about by changes in the
Th17/Treg balance, and increased basal levels of various pro‐inflammatory cytokines.
Testosterone, the Immune System, and Aging
Testosterone is a steroid hormone that has been shown to have anti‐
inflammatory properties. It has been shown to be protective in a mouse model of
rheumatoid arthritis, which is an autoimmune disease, through the downregulation of
autoantibodies (Keith et al., 2013). Testosterone also decreased IFN‐γ production from
natural killer T (NKT) cells in a mouse model of amebic liver abscess, which is caused by
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infection with Entamoeba histolytica (Lotter et al., 2013). In a study of influenza,
gonadectomized male mice showed reduced survival when infected with a lethal dose
of the virus, without showing any change in viral titers relative to infected gonadally‐
intact mice, suggesting that testosterone has a protective effect on disease outcome
through modulating the immune response against the virus (Robinson et al., 2011). High
testosterone in men is associated with lower antibody titers in response to influenza
vaccination (Furman et al., 2014).
Testosterone can act directly on androgen receptors present in CD4+ T cells to
increase the production of the anti‐inflammatory cytokine IL‐10 (Liva et al., 2001). It also
suppresses the generation of reactive oxygen species and IL‐8 in human granulocytes
and monocytes (Boje et al., 2012). Reactive oxygen species are involved in the induction
of an inflammatory response, and IL‐8 is a chemokine that directs neutrophils and other
granulocytes to the site of damage or infection.
Preliminary research from our lab has shown that testosterone has a protective
effect on the disease pathology caused by Influenza A virus infection in male mice.
Administration of exogenous testosterone to gonadectomized young male mice resulted
in less weight loss, which is a measure of disease pathology, in response to influenza
infection compared to gonadectomized mice treated with placebo only. Clinical scoring
of observable symptoms of disease also showed a protective effect of testosterone on
observable morbidity from influenza infection. Influenza disease is mainly caused by
immune‐mediated pathology in response to the virus (Damjanovic et al., 2012), so the
8
anti‐inflammatory properties of testosterone are thought to be responsible for its
protective effects against influenza disease pathology.
Testosterone in males decreases with age in both humans (Maggio et al., 2005)
and rodents (Coquelin & Desjardins, 1982). Old male mice infected with influenza
exhibit lower survival rates than young male mice, which we hypothesize to suggest that
testosterone may have a protective effect against influenza disease in young mice. Low
testosterone in old males may lead to immune dysregulation as a result of the loss of
the anti‐inflammatory effects of testosterone seen in younger males. The hormone
leptin also may play a role in the increased inflammation seen in old males. It is required
for the proliferation of activated CD+ T cells, which are important mediators of
inflammation upon infection (Saucillo et al., 2014). Leptin has been shown to be
elevated in populations with low testosterone such as women, older men, (Furman et
al., 2014), and men treated with cetrorelix, which reversibly reduced testosterone to
castrate levels (Büchter et al., 1999).
We hypothesize that the chronic pro‐inflammatory state associated with aging in
men is therefore possibly partially linked to a decrease in testosterone levels. This is
supported by data showing the interaction of testosterone with the immune system and
the outcome of infectious diseases (Liva et al., 2001; Keith et al., 2013). For diseases
such as influenza, that are primarily caused a dysregulated inflammatory response
(Damjanovic et al., 2012), decreased testosterone may result in more severe disease
9
pathology in the elderly, despite the general decline of immune function with age
(Castelo‐Branco & Soveral, 2014).
Models for Studying the Effects of Testosterone in Old Male Mice
The mouse model that we use for studying the effects of testosterone requires
the subcutaneous implantation of silastic capsules containing crystalline testosterone
propionate (TP) between the scapulae of the mice, which results in the slow release of
testosterone into the bloodstream (Hetzler et al., 2008). The length of the capsule
determines the rate of release of testosterone. Previous research in our lab has utilized
this model to show the protective effects of testosterone against influenza disease from
infection with maPR8 influenza in castrated young male mice (introduce in results). In
old male mice, studies have been conducted using exogenous administration of
testosterone in non‐castrated mice to observe the effects of testosterone on androgen
receptor expression, anti‐anxiety behavior, and cognitive performance (Hill et al., 2004;
Frye et al., 2008). This is made possible because old male mice have low endogenous
(Sigma), or Ro5‐4864: 7‐chloro‐5‐(4‐chlorophenyl)‐1,3‐dihydro‐1‐methyl‐2H‐1,4‐
benzodiazepin‐2‐one (Sigma). Each experimental group was injected with either 3 mg/kg
or 0.3 mg/kg of either PK 11195 or Ro5‐4864 dissolved in 10% dimethylsulphoxide
(DMSO) and 90% PBS with Ca+ and Mg+. The control group was injected with the vehicle
solution alone.
Testosterone Administration
Testosterone (T) was administered by subcutaneously implanting a silastic
capsule (0.040 inch inner diameter id, 0.085 inch outer diameter, 12.5 mm and 20 mm
length for 7.5 mm T capsules and 15 mm T capsules respectively) between the scapulae,
containing 100% crystalline testosterone propionate (Sigma) as previously described
(Hetzler et al., 2008). The capsules were enclosed by 2.5 mm of medical adhesive on
both ends, and equilibrated in sterile physiological saline. The 7.5 mm T capsules have
been shown to produce serum testosterone levels approximating the higher end of the
14
physiological range in young male C57BL/6 mice for at least 28 days post implantation
(unpublished data). Animals in the untreated group were similarly anesthetized and
received implants of blank capsules.
Sample Collection
Body mass was recorded daily for 14 days in the ligand pilot study, and body
mass, and body temperature were recorded daily for 21 days and clinical scores were
recorded at various time points in the influenza morbidity studies. Clinical scores were
adapted from the SHIRPA primary screen, and morbidity from influenza in the mice
were assigned a total of scores of 0 or 1 for hyperapnea, piloerection, hunched, and no
escape, and 5 for death. In the ligand pilot study, serum was collected on days 3 and 7,
and stored at ‐80C until they were thawed for serum testosterone measurement by
radioimmunoassay as previously described. The mice were euthanized on day 7, and
seminal vesicles and testes were collected to weigh, and to weigh and measure
testicular testosterone, respectively. In the morbidity studies, mock and influenza‐
infected males were euthanized at one of several days post‐infection (dpi), at which
time, serum was collected to measure antibody titers, and whole lungs were either
snap‐frozen and stored at ‐80C to measure viral titers, or inflated with Z‐fix to observe
inflammation by immunohistochemistry as described below.
Immunohistochemistry and Staining
Lungs were inflated, fixed in Z‐fix, embedded in paraffin, cut into 5 μm sections,
15
and mounted on glass slides. Slides were deparafinized with xylene and rehydrated in
graded ethanol. Heat‐induced antigen retrieval with citrate buffer was performed and
slides were blocked with 10% normal goat serum prior to overnight incubation with the
primary antibody in a humidified chamber. The slides were then treated with 3%
hydrogen peroxide to block endogenous peroxidase activity. Detection of the primary
antibody signal was done using the EXPOSE rabbit specific HRP/DAB detection kit
(abcam). Primary antibodies included: rabbit anti‐Ki67 (Abcam), anti‐IAV NA antibody.
Images were taken using a Nikon Eclipse E800 and analyzed using ImageJ (NIH).
Anti‐influenza total IgG ELISA
ELISA plates (96 well, company here) were coated overnight at 4°C with 100 ng
of purified ma2009 H1N1, after which plates were washed and blocked for 1 h with
blocking solution (10% dry skim milk powder in PBS). Plates were washed, duplicate
diluted serum samples were added in a 2‐fold series starting at 1:1000, and plates were
incubated at 37°C for 1 h. Anti‐mouse IgG secondary antibody (1:5000; Peroxidase
AffiniPure Goat Anti‐mouse IgG; Jackson Immunoresearch Laboratories) was added and
plates were incubated for 1 h at 37°C. Reactions were developed with 3,3’,5,5’
tetramethylbenzidine (TMB) and stopped using 1N HCL. Plates were read at 450 nm
absorbance on a plate reader. To determine the antibody titer, a cutoff value was
determined by multiplying the average ELISA values of serum from naïve animals at
each dilution by 3. The sample ELISA titer was the highest serum dilution of that sample
series with a value above the cutoff. A sample was considered positive only if the
16
average OD was 3 times higher than the corresponding dilution value of naïve serum.
Statistical Analyses
Morbidity data were analyzed with a multivariate analysis of variance (MANOVA)
with one within‐subjects variable (days) and one between‐subjects variable (treatment)
and significant interactions were further analyzed using planned comparisons. Serum
proteins, organ weights, virus titers, and IHC data were analyzed using one‐way ANOVA
or t tests, significant interactions were further analyzed using the Tukey method for
pairwise multiple comparisons. Mean differences were considered statistically
significant if p<0.05.
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RESULTS
Administration of testosterone results in reduced morbidity and antibody
titers in young male mice following infection with influenza A virus
Young male C57BL/6 mice were gonadectomized and implanted with placebo
capsules or 7.5 mm testosterone propionate capsules, which elevate serum
testosterone to the upper limit of the physiological range observed in intact young male
mice (Fig. 1A). Following infection with ma2009 H1N1 influenza A virus, testosterone‐
treated mice showed reduced percentage loss of body mass (Fig. 1B), and had a lower
clinical disease score of observable symptoms (Fig. 1C) compared to placebo‐treated
mice. Antibody titers in serum samples collected at day 21 post infection were lower for
the testosterone‐treated mice compared to the placebo‐treated mice (Fig. 1D). These
data suggest that treatment with testosterone affects the outcome of influenza, at least
in young male mice.
Administration of the TSPO Ligands Ro5‐4864 and PK11195 does not
increase testosterone concentrations in old male mice
Testosterone concentrations decline with age, even in mice (Coquelin &
Desjardins, 1982). To test the hypothesis that endogenous testosterone levels can be
increased in old male mice, old male C57BL/6 mice were treated with high (3 mg/kg) or
low (0.3 mg/kg) doses of Ro5‐4864 or PK11195, or vehicle. The mice were weighed daily
for the seven day duration of the treatment to determine if TSPO ligands cause notable
18
toxicity. Treatment with TSPO ligand did not change body mass relative to vehicle‐
treated males (Fig. 2A). Mice treated with the low dose (0.3 mg/kg) of either TSPO
ligand (Ro5‐4864 and PK11195) showed an increase in seminal vesicle mass relative to
those treated with the high doses (3 mg/kg) of TSPO ligands or vehicle for 7 days (Fig.
2B). Despite the observed changes in seminal vesicle mass, which is androgen‐
dependent, there was no significant increase in serum testosterone concentrations after
treatment with either low or high doses of either TSPO ligand after either 3 or 7 days of
treatment (Fig. 2C,D). Similarly, testicular production of testosterone was not
significantly elevated by treatment with TSPO ligands (Fig. 2E). These data suggest that
TSPO ligands, at least at the tested doses, are not sufficient to elevate testosterone in
old male mice.
Administration of low dose testosterone does not alter the outcome of
infection with ma2009 H1N1 in old male mice
To test the hypothesis that exogenous elevation of testosterone in old males will
improve influenza pathogenesis, old male C57BL/6 mice were left intact and implanted
with placebo capsules or 7.5 mm (low dose) testosterone propionate capsules, which
elevate serum testosterone to the upper limit of the physiological range observed in
intact young male mice (Fig. 3A). Following infection with ma2009 H1N1, low dose
testosterone‐treated mice showed no change in percentage loss of body mass (Fig. 3B)
or survival (Fig. 3C) compared to placebo‐treated mice. The average day of death after
19
infection was slightly later for the testosterone‐treated (15±3.00) compared with
placebo‐treated (11.7±1.20) mice. Antibody titers in serum samples collected at day 28
post infection were similarly low between the low dose testosterone‐treated mice and
the placebo‐treated mice (Fig. 3D). These data suggest that old male mice may be less
responsive to testosterone treatment than their young male counterparts, at least with
regard to influenza virus infection.
Administration of high dose testosterone improves the outcome of
infection with ma2009 H1N1 in old male mice
To test the hypothesis that old male mice require higher doses of testosterone to
alter the outcome of influenza infection, old male C57BL/6 mice were left intact and
implanted with placebo capsules or 15 mm (high dose) testosterone propionate
capsules. Serum testosterone concentrations were not significantly increased at 21 days
after infection (28 days after implantation) (Fig. 4A). Following infection with ma2009
H1N1 influenza A virus, high dose testosterone‐treated mice showed reduced
percentage loss of body mass (Fig. 4B), but similar survival (Fig. 4C) compared to
placebo‐treated mice. The average day of death after infection was slightly later for the
testosterone‐treated (13.8±2.03) compared with placebo‐treated mice (12±0.68).
Antibody titers in serum samples collected at day 21 post infection were similarly low
between the high dose testosterone‐treated mice and the placebo‐treated mice (Fig.
20
4D). These data suggest that testosterone treatment can improve outcome measures of
influenza virus infection.
Protection from influenza pathogenesis is not associated with increased
proliferation in the lungs at 21 days post infection
Testosterone (T) treatment in young male mice (with 7.5 mm T capsules), and
old male mice (with 15 mm T capsules) was protective against morbidity from influenza
virus infection. To test the hypothesis that this was due to increased repair in the
testosterone‐treated mice, we measured the expression of Ki67, which is a marker for
cellular proliferation, in the lungs at 21 days after infection. There was no significant
difference in Ki67 expression between placebo‐treated and testosterone‐treated young
male mice, and between placebo‐treated and high dose testosterone‐treated old male
mice (Fig. 5B). These data suggest that there is either no effect of testosterone on
repair, or the effect can be better detected at an earlier time point.
21
Figure 1: Effects of testosterone (T) on the outcome of ma2009 H1N1 influenza
infection in young male mice (2 mo). Young male mice were gonadectomized (gdx) and
implanted with 7.5 mm T (n=15) or placebo (n=14) capsules. Serum T was measured by
RIA (A), body mass was measured daily (B), and clinical scores were measured on days 0,
3, 5, 7, 9, 11, 14, and 18 post infection (C). Antibody titers were analyzed 21 days post
infection by ELISA (D). Data shown are the mean ± SEM. Asterisks (*) denote p<0.05.
Red lines in panel A represent physiological serum T range in young male mice.
Figure 1
22
A. B.
D. C.
E.
Figure 2
23
Figure 2: Effects of Ro5‐4864 and PK11195 on body mass, and serum and testicular
testosterone (T) in old male mice. Old male mice received either Ro5‐4864 or PK11195
[low (L): 0.3 mg/kg body mass; high (H): 3 mg/kg body mass] or placebo by ip injection
for 7 days (n=5 in each group). Body mass was measured daily over the course of the
seven day study (A). Seminal vesicle mass was measured after 7 days, and data is
presented as a percentage of total body mass of each mouse (B). Serum T at days 3 (C)
and 7 (D), and testicular T (D) were measured by RIA. Data shown are the mean ± SEM.
*P < 0.05. Red lines in panel C and D represent physiological serum testosterone range
in young male mice.
24
Figure 3: Effects of low dose testosterone (low T) on the outcome of ma2009 H1N1
influenza infection in old male mice (17 mo). Old male mice were implanted with low T
(n=10) or placebo capsules (n=9). Serum T was measured by RIA (A), body mass was
measured daily (B), and survival was assessed using the Kaplan‐Meier method (C).
Antibody titers were analyzed 28 days post infection by ELISA (D). Data shown are the
Figure 3
25
mean ± SEM. Asterisks (*) denote p<0.05. Red lines in panel A represent physiological
serum T range in young male mice.
26
Figure 4: Effects of high dose testosterone (high T) on the outcome of ma2009 H1N1
influenza infection in old male mice (17 mo). Old male mice were implanted with high T
or placebo capsules (n=17 in each group). Serum T was measured by RIA (A), body mass
was measured daily (B), and survival was assessed using the Kaplan‐Meier method (C).
Antibody titers were analyzed at 21 days post infection by ELISA (D). Data shown are the
mean ± SEM. Asterisks (*) denote p<0.05. Red lines in panel A represent physiological
serum T range in young male mice.
Figure 4
27
Placebo T‐Treated
Young
Old
Figure 5
A.
B.
28
Figure 5: Effects of testosterone treatment on ki67 expression 21 days post infection
with ma2009 H1N1 influenza in young and old male mice. Paraffin‐embedded lungs
were deparafinized and stained with anti‐Ki67 antibody and DAB substrate (brown) and
counterstained with hematoxylin (purple). Representative images are provided for lungs
from young and old placebo and testosterone‐treated male mice (A). Percentage of
Ki67+ nuclei was calculated in lungs tissue from young and old placebo and
testosterone‐treated male mice (n=3 in each group) (B). Arrows indicate Ki67 positive
staining.
29
DISCUSSION
Conclusions
Age‐related changes in immune function result in more severe disease from
influenza infection in the elderly (Parzych et al., 2013). Because influenza disease
pathology is primarily mediated by a dysregulated inflammatory response (Damjanovic
et al., 2012), this is possibly influenced by the chronic pro‐inflammatory state associated
with aging, which results in higher basal levels of pro‐inflammatory cytokines and may
contribute to more severe disease in the elderly (Cannizzo et al., 2011). Compared to
elderly females, as well as young males, elderly males are more susceptible to severe
disease (Serfling et al., 1967). Testosterone has been shown to have anti‐inflammatory
properties in various models (Keith et al., 2013; Lotter et al., 2013), and decreasing
levels of testosterone with age in men (Maggio et al., 2005) could contribute to the
increased severity of disease in elderly men. Therefore, we hypothesized that
testosterone administration would be protective against influenza disease in our mouse
model of influenza by modulating the inflammatory response to infection.
We assessed the effects of testosterone in young male mice to confirm that
testosterone affects influenza pathogenesis. Administration of testosterone (7.5 mm)
and restoration of serum testosterone to the upper end of physiological levels was
protective against morbidity from infection with ma2009 H1N1 influenza A virus in
gonadectomized young male mice. These results are consistent with reports in the
30
literature of the anti‐inflammatory properties of testosterone (Keith et al., 2013; Lotter
et al., 2013), as well as previous research from the lab using maPR8 H1N1 influenza
virus, which showed that gonadectomized young male mice showed lower survival than
intact young male mice in response to a lethal dose of virus without observing any
differences in viral titers (Robinson et al., 2011). Antibody titers were significantly lower
in the serum collected at day 21 from the testosterone‐treated mice, which further
points towards an immunosuppressive role for testosterone. This replicates findings in a
study conducted with human populations that showed that men with higher
testosterone levels produce a lower antibody response in response to a trivalent
inactivated influenza vaccine compared to men with lower testosterone (Furman et al.
2014).
Old male mice have lower testosterone levels as compared with younger male
mice (Coquelin & Desjardins, 1982). In order to determine whether testosterone is
protective in old male mice, we first looked at a means of raising testosterone levels
endogenously, as that could be an alternative to directly administering testosterone to
elderly males. TSPO ligands have been shown to raise testosterone to physiological
levels in old male rats by stimulating steroidogenesis in the testes (Chung et al., 2013).
We hypothesized that the same would be true in old male mice. However,
administration of two different TSPO ligands, Ro5‐4864 and PK11195, in high or low
doses did not significantly raise either testicular or serum testosterone levels in old male
C57BL/6 mice. While the trending association between low dose TSPO ligand and higher
serum testosterone may reach statistical significance with a larger sample, none of the
31
groups showed testosterone elevated to within the physiological range of testosterone
observed in healthy young mice. However, the mice treated with low doses of the
ligands showed a significant increase in seminal vesicle mass, providing some evidence
that these TSPO ligands have a greater physiological effect at low than high doses. The
dose response of the drug does not appear to be linear, therefore it is difficult to
determine whether a higher or lower dose of TSPO ligand would increase testosterone
to a greater extent. A possible reason for TSPO ligands raising testosterone levels in rats
but not in mice may be differences in binding with the TSPO protein. We therefore
decided that TSPO ligand would not serve as an effective model to study the effects of
testosterone on influenza pathogenesis in old male C57BL/6 mice. For that, we reverted
to our model of testosterone replacement using capsules as in young male mice.
Aging results in an overall decline in immune function (Castelo‐Branco & Soveral,
2014), as well as an increase in the basal levels of pro‐inflammatory cytokines (Cannizzo
et al., 2011). Whether age‐related changes in immune function could be reversed by
treatment with testosterone was tested. In contrast to the data from young male mice
showing that lower testosterone is associated with higher antibody titers, older male
mice produced lower antibody titers than younger male mice, regardless of whether
they were treated with testosterone. This suggests that vaccines would not be as
effective in elderly individuals, and this is consistent with studies conducted on influenza
vaccine efficacy in humans (Sasaki et al., 2011). Decreased antibody responses resulting
from both aging and testosterone administration in young male mice indicate the need
for tailoring vaccinations to specific population subsets to ensure sufficient protection.
32
Administration of low dose testosterone, despite elevating serum testosterone
to the upper end of physiological levels seen in young male mice, was not protective
against morbidity or survival from infection with ma2009 H1N1 influenza A virus in old
male mice. This is possibly a result of the chronic pro‐inflammatory state associated
with aging (Cannizzo et al., 2011), which may not be counteracted sufficiently by the
same dose of testosterone that was protective in young male mice. It is also possible
that aging results in a decrease in androgen receptor expression, which would limit the
effects of testosterone. Administration of high dose testosterone was protective against
morbidity but not survival from infection with ma2009 H1N1 influenza A virus in old
male C57BL/6 mice. However, testosterone levels in the high dose testosterone‐treated
mice had been depleted to levels comparable to placebo‐treated mice 28 days after
implantation (21 days post infection). We hypothesize that this is because testosterone
in the high dose capsules diffused out at a faster rate as a result of an increased surface
area compared to that of the low dose capsules. The protection against morbidity from
influenza pathogenesis in the high dose testosterone‐treated group despite the early
depletion of the hormone in the serum suggests that testosterone may be having an
early effect on the immune response to the virus, and resulting in downstream
protective effects. This is consistent with a study showing that testosterone
downregulates the expression of toll‐like receptor 4 (TLR‐4) in macrophages in mice;
TLR‐4 is a key trigger for inflammation and innate immunity. Both doses of testosterone
resulted in a trend of delay in the average day of death, again suggesting a protective
effect.
33
None of the treatment groups of old male mice fully recovered to baseline body
mass after infection, which is consistent with evidence in the literature suggesting that
aging results in decreased recovery from influenza infection (Yin et al., 2014). However,
high dose testosterone resulted in significantly improved recovery, which suggests that
testosterone is one of several factors that can influence the outcome of influenza
disease in old male mice, and that the higher dose of testosterone is sufficient in
counteracting some of the excessive inflammation that is associated with the disease.
Testosterone has been shown to accelerate repair in other models of injury (Hetzler et
al., 2008). We therefore hypothesized that decreased morbidity from influenza virus
infection in testosterone‐treated young male mice and high dose testosterone‐treated
old male mice might partially be influenced by increased repair in the lungs after
infection. However, our data from 21 days after infection does not suggest that is the
case. It may possibly be more useful to look at ki67 at earlier time points during and
before peak of disease according to the morbidity curves, in order to more accurately
assess a role for repair in the protective effect of testosterone against morbidity from
influenza virus infection.
Future Directions
The lower dose of testosterone, despite increasing serum testosterone levels in
old male mice to the upper levels of the physiological range of testosterone seen in
young male mice, did not have the same protective effect against morbidity as in the
34
young male mice. To test whether this is because of a decrease in androgen receptor
(AR) expression with age, we will measure AR expression in young and old male mice
with and without testosterone treatment.
The depletion of testosterone at 21 days post infection is a limitation to the
interpretation of this data as maintaining a constant environment of elevated
testosterone is important to our hypothesis. To have a more concrete understanding of
what part of the response to influenza virus infection is being affected by testosterone,
we will determine the time after implantation of the high dose testosterone capsules at
which serum testosterone peaks and how long it takes to be depleted after that. We will
collect serum at various time point post infection, and measure testosterone.
We hypothesized that the protection from influenza pathogenesis in
testosterone‐treated young male mice and high dose testosterone‐treated old male
mice is possibly a repair of accelerated repair in the lungs, as testosterone has been
shown to upregulate repair in other models of injury (Hetzler et al., 2008). At 21 days
after infection, we do not see a difference in expression of Ki67, which is a marker for
proliferation, between lungs from placebo‐treated and testosterone‐treated mice
among both young and old age groups. As day 21 is after peak infection and viral
clearance (Robinson et al., 2011), it is possible that it is too late to detect a difference at
this point. We will therefore measure Ki67 expression in lungs at days 7 and 14 post
infection to detect a possible difference in epithelial repair at earlier time points during
the infection.
35
Public Health Significance
Influenza is a global public health burden. Seasonal influenza is a significant
cause of mortality every year (Lagace‐Wiens et al., 2010). Owing to the mutation‐prone
nature of its RNA genome (Lauring et al., 2013), new vaccines need to be researched
and manufactured every year to combat the spread of the virus in the population. While
seasonal strains are not always severe, influenza can result in hospitalizations and
death, especially in at‐risk populations, including the elderly (Mauskopf et al., 2013).
Elderly men, in particular, tend to be more susceptible to severe disease compared to
elderly women and young men (Serfling et al., 1967). This, combined with the fact that
elderly men produce lower antibody titers than elderly women in response to influenza
vaccination makes influenza a serious threat for elderly men (Sasaki et al., 2011).
Low testosterone and its accompanying effects are also a significant burden
among elderly men (Maggio et al., 2005). It is possibly associated with the increased
severity of influenza in elderly men, as testosterone has been shown to have anti‐
inflammatory properties (Lotter et al., 2013), and severe pathology from influenza is
known to be caused by an excessive inflammatory response to infection (Damjanovic et
al., 2012). We therefore hypothesized that testosterone administration may provide
some protection for elderly men against influenza pathogenesis.
We utilized old male mice with low testosterone as our model for elderly men in
the population. Our results suggest that testosterone could be useful in decreasing
morbidity from influenza, but further research is required to elucidate the mechanisms
36
of this protection, and to determine any possible side effects of immunomodulation by
testosterone.
37
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44
Ornob Alam
Home: 1024 North Broadway St. Baltimore, Maryland, 21205 E: [email protected] P: (850) (570)‐0594 Work: Department of Molecular Microbiology and Immunology 615 North Wolfe St. Baltimore, Maryland, 21205 E: [email protected] P: (410) 614‐7794 Born: 9th February, 1991, Dhaka, Bangladesh Nationality: USA Education: B.Sc. in Biological Science from Florida State University, Tallahassee, FL (August 2009‐May 2013), GPA 3.70/4.00. Sc.M. Candidate in Molecular Microbiology & Immunology at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD (September 2013‐present), GPA 3.62/4.00. Thesis Title: The Effects of Elevated Testosterone on the Outcome of ma2009 H1N1 Influenza A Virus Infection in Old Male Mice. Thesis Advisor: Dr. Sabra Klein. Anticipated to graduate in May 2014 Professional Experience: Undergraduate Research. Dr. David Gilbert’s laboratory at Florida State University (January 2012‐May 2013). Principal responsibilities included BAC and plasmid purification, molecular cloning, and genetic recombineering Sc.M. Research. Dr. Sabra Klein’s laboratory at Johns Hopkins Bloomberg School of Public Health (September 2014‐present). Principal responsibilities include conducting animal studies, including infection, dissection and tissue collection as well as assays including virus titration, ELISAs, virus neutralization, radioimmunoassays, and immunohistochemistry
45
Volunteer Experience: UMAR Boxing. Tutored, and organized volunteering trips for children in an after‐school program (January 2014‐May 2014) Art With a Heart. Co‐instructed a summer art class for middle‐school children across five schools in Baltimore (June 2014‐August 2014) Presentations: 2012 Undergraduate Research and Creative Activities Awards Symposium. “Is Late Replication Necessary for G9a‐Mediated Methylation to Occur?” Awards: 2012 Undergraduate Research and Creative Activities Award Skills: Laboratory Techniques: BAC and plasmid purification; molecular cloning; genetic recombineering; DNA and RNA extractions; animal studies, including infection, dissection, tissue collection, and behavioral phenotyping; virus titration; ELISAs; virus neutralization; radioimmunoassays; immunohistochemistry Statistical Analyses: Systat, SigmaPlot, Prism, Stata Languages Spoken: Bengali, Hindi, English References: Sabra L. Klein, PhD Associate Professor Department of Molecular Microbiology and Immunology Johns Hopkins Bloomberg School of Public Health 615 N. Wolfe Street Baltimore, Maryland 21205 P: (410)955‐8898 E: [email protected] Andrew Pekosz, PhD Associate Professor Department of Molecular Microbiology and Immunology Johns Hopkins Bloomberg School of Public Health 615 N. Wolfe Street
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Baltimore, Maryland 21205 P: (410) 502‐9306 E: [email protected] David Gilbert, PhD J. Herbert Taylor Distinguished Professor of Molecular Biology Department of Biological Science Florida State University 319 Stadium Drive Tallahassee, Florida 32306 P: (850) 645‐7583 E: [email protected]